Preparation

Preheat oven to 350 degrees F and spray 8 x 8 cake pan with cooking spray. In a large bowl, whisk together the brown sugar, eggs, baking soda, and salt. Stir in yogurt, vanilla and oil. Add flour and stir with a spatula until just combined. Spread half of the batter into the prepared baking pan. Sprinkle the frozen Wild Blueberries over the batter. Spoon the rest of the batter into the pan.

Place crumble ingredients into small bowl. Using your fingers, squeeze the cold butter into the flour and sugar until it forms small pieces. Sprinkle the crumble mixture generously over the cake until the entire batter is covered. Bake until a knife inserted into the center comes out clean, about 20-22 minutes. Let cool slightly and then transfer to a cooling rack. Cut into 2-inch squares and serve warm.